An evaluation of geographic and annual variation in morphometric characters and gill-raker counts of yellowfin tuna, Thunnus albacares, from the Pacific Ocean

Schaefer, Kurt M. (1992) An evaluation of geographic and annual variation in morphometric characters and gill-raker counts of yellowfin tuna, Thunnus albacares, from the Pacific Ocean. Inter-American Tropical Tuna Commission Bulletin, 20(3), pp. 133-163.

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Abstract

ENGLISH: Samples of yellowfin tuna, Thunnus albacares, collected from five areas of the Pacific Ocean (Mexico, Ecuador, Australia, Japan, and Hawaii) between January and May of 1988 and 1990 were examined for spatiotemporal variation in morphometric characters and gill-raker counts. 'Iwo-factor analysis of variance, with area and year treated as grouping factors, indicated a significant difference in the means of the total gill-raker counts among fish from different areas, but no significant difference between fish caught in different years. The morphometric data were adjusted by allometric formulae to remove size effects. The correct classification rates for the five groups, using discriminant function analysis, based on adjusted morphometric characters, were 77.60/0 for the samples from 1988 and 74.40/0 for those from 1990. These are 72.00/0 and 68.00/0 (Cohen's kappa statistic) better than would have occurred chance. The pattern of geographic variability, however, is unstable for these two years, thus requiring separate discriminant functions for each year. Although there is annual variability in the morphometric characters, these results demonstrate that the stocks examined are morphometrically distinguishable and that their phenetic relationships reflect their geographic origin. SPANISH: Se examinaron muestras de atún aleta amarilla, Thunnus albacares, tomadas de cinco áreas del Océano Pacífico (México, Ecuador, Australia, Japón, y Hawaii) entre enero y mayo de 1988 y 1990, para descubrir variaciones espaciotemporales en las características morfométricas y los conteos de branquiespinas. Un análisis de varianza de dos factores, con área y año como factores de agrupación, indicó una diferencia significativa en los promedios de los conteos de branquiespinas totales entre peces de distintas áreas, pero ninguna entre peces capturados en distintos años. Se ajustaron los datos morfométricos con fórmulas alométricas para eliminar los efectos de la talla del pez. En un análisis de función discriminante, las tasas de clasificación correcta de los cinco grupos, basadas en características morfométricas ajustadas, fueron 77.60/0 para las muestras de 1988 y 74.40/0 para aquellas de 1990. Estas cifras son 72.00/0 y 68.00/0 (estadístico de kappa de Cohen) mejores de lo que se hubiera obtenido al azar. Sin embargo, la variabilidad geográfica es inestable en estos dos años, requiriendo por lo tanto funciones discriminantes separadas para cada año. Aunque existe variabilidad anual en las características morfométricas, estos resultados demuestran que los stocks examinados son morfamétricamente distinguibles, y que su relación fenética refleja su origen geográfico. (PDF contains 31 pages.)

Item Type: Article
Title: An evaluation of geographic and annual variation in morphometric characters and gill-raker counts of yellowfin tuna, Thunnus albacares, from the Pacific Ocean
Personal Creator/Author:
CreatorsEmail
Schaefer, Kurt M.
Journal or Publication Title: Inter-American Tropical Tuna Commission Bulletin
Volume: 20
Number: 3
Page Range: pp. 133-163
Date: 1992
Issuing Agency: Inter-American Tropical Tuna Commission
Additional Information: This article is bilingual and contains both Spanish and English translations.
Uncontrolled Keywords: geographic variation; annual variation; morphometric characters; gill-raker counts; yellowfin tuna; Thunnus albacares; Pacific Ocean; variación geográfica; variacion anual; características morfometricas; conteos de branquistinas; atun aleta amarilla; Océano Pacifico
Subjects: Fisheries
Item ID: 3495
Depositing User: Joan Parker
Date Deposited: 04 Jun 2010 07:08
Last Modified: 29 Sep 2011 17:18
URI: http://aquaticcommons.org/id/eprint/3495

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